U.S. patent application number 13/545307 was filed with the patent office on 2012-11-01 for methods and apparatus for using multiple antennas having different polarization.
This patent application is currently assigned to QUALCOMM Incorporated. Invention is credited to Vikram Reddy Anreddy, Xinzhou Wu.
Application Number | 20120275499 13/545307 |
Document ID | / |
Family ID | 40945757 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120275499 |
Kind Code |
A1 |
Anreddy; Vikram Reddy ; et
al. |
November 1, 2012 |
METHODS AND APPARATUS FOR USING MULTIPLE ANTENNAS HAVING DIFFERENT
POLARIZATION
Abstract
A MIMO wireless communications device supports a dual polarized
mode of antenna operation and a single polarized mode of antenna
operation. Antenna mode selection is performed as a function of
signal to noise ration information and/or rank information
corresponding to a communications channel matrix. One of a
communications device's processing chains is switched between first
and second polarization orientation antennas, e.g., vertical and
horizontally polarized antennas, as a function of the antenna mode
selection. In various embodiments, the dual polarized mode is
advantageously used for high SNR users, while in the low SNR
regime, where the capacity is limited by received power, the single
polarized antenna configuration, sometimes referred to as the
spatial MIMO configuration, is used.
Inventors: |
Anreddy; Vikram Reddy;
(Bridgewater, NJ) ; Wu; Xinzhou; (Monmouth
Junction, NJ) |
Assignee: |
QUALCOMM Incorporated
San Diego
CA
|
Family ID: |
40945757 |
Appl. No.: |
13/545307 |
Filed: |
July 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12032454 |
Feb 15, 2008 |
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13545307 |
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Current U.S.
Class: |
375/219 ;
342/361; 375/227; 375/295; 375/340 |
Current CPC
Class: |
H04B 17/336 20150115;
H04B 7/0689 20130101; H04B 7/10 20130101; H04B 7/0805 20130101;
H04B 7/04 20130101; H04B 7/0602 20130101 |
Class at
Publication: |
375/219 ;
375/340; 375/295; 375/227; 342/361 |
International
Class: |
H04B 1/38 20060101
H04B001/38; H04B 7/10 20060101 H04B007/10; H04B 17/00 20060101
H04B017/00; H04L 27/06 20060101 H04L027/06; H04L 27/04 20060101
H04L027/04 |
Claims
1. A communications device comprising: a first antenna element
polarized in a first direction; a second antenna element polarized
in a second direction, the second direction being different from
the first direction by at least 45 degrees; a first signal
processing module coupled to the first antenna element; and a
second signal processing module coupled to the second antenna
element.
2. The communications device of claim 1, wherein the first signal
processing module and the second signal processing module are
configured to recover data from a first received signal and a
second received signal, the first received signal having a
frequency that is the same as the frequency of the second received
signal, and the first received signal having a first polarization
different from a second polarization of the second received
signal.
3. The communication device of claim 1, wherein the first signal
processing module and the second signal processing module are
configured to generate a first transmission signal and a second
transmission signal, the first transmission signal having a
frequency that is the same as the frequency of the second
transmission signal, and the first transmission signal having a
first polarization different from a second polarization)f the
second transmission signal.
4. The communications device of claim 1, further comprising: a
third antenna element polarized in the first direction; an antenna
switching module configured to couple the second antenna element
and the third antenna element to the second signal processing
module, the antenna switching module selectively passing signals
between the second processing module and one of the second antenna
element and the third antenna element at any given time.
5. The communications device of claim 4, further comprising: a
channel quality determination module for generating channel quality
indicators from received signals, the channel quality indicators
including a signal to noise ratio value.
6. The communications device of claim 5, further comprising: a
channel quality information transmission control module for
controlling transmission of channel quality information including
the signal to noise ratio value and rank information for a channel
matrix between transmitter antennas used to transmit to the
communications device and receive antennas included in the
communications device having a polarization which is the same as
the transmitter antennas.
7. The communications device of claim 6, further comprising: an
antenna mode indicator signal detection module for detecting
receipt of an antenna mode indicator signal and for recovering
information indicating one of a dual polarized mode of operation
and a single polarized mode of operation.
8. The communications device of claim 5, further comprising: an
antenna mode selection module for selecting between a dual
polarized mode of operation and a single polarized mode of
operation as a function of the generated channel quality
indicators.
9. The communications device of claim 8, further comprising: an
antenna mode indicator signal generation module for generating a
signal indicating the selected antenna mode of operation; and an
antenna mode indicator signal transmission control module for
controlling transmission of the antenna mode indicator signal.
10. The communications device of claim 5, wherein the antenna
switching module is configured to couple the second antenna element
to the second signal processing module when the dual polarized mode
of operation is selected; and wherein the antenna switching module
is configured to couple the third antenna element to the second
signal processing module when the single polarized mode of
operation is selected.
11. The communications device of claim 10, wherein the first
direction is a vertical direction; and wherein the second direction
is a horizontal direction.
12. The communications device of claim 2, further comprising: an
antenna mode selection module for selecting between a dual
polarized mode of operation and a single polarized mode of
operation as a function of received channel quality information;
wherein the first received signal and the second received signal
are received through the first antenna element and the second
antenna element when the dual polarized mode of operation is
selected; and wherein the first received signal and the second
received signal are received through the first antenna element and
the third antenna element when the single polarized mode of
operation is selected.
13. The communications device of claim 2, further comprising: an
antenna mode selection module for selecting between a dual
polarized mode of operation and a single polarized mode of
operation as a function of received channel quality information;
wherein the first transmission signal and the second transmission
signal are transmitted through the first antenna element and the
second antenna element when the dual polarized mode of operation is
selected; and wherein the first transmission signal and the second
transmission signal are transmitted through the first antenna
element and the third antenna element when the single polarized
mode of operation is selected.
14. The communications device of claim 2, wherein the
communications device is a transceiver, the communications device
further comprising: a transmitter/receiver mode control module for
controlling whether the communications device operates in a
transmit or receive mode of operation; and an antenna mode
selection module for selecting between a dual polarized mode of
operation and a single polarized mode of operation as a function of
a received indicator signal, wherein the antenna mode selection
module selects the dual polarized or single polarized mode of
operation based on the antenna mode indicator signal.
15. The communications device of claim 14, wherein the received
indicator signal is an antenna mode indicator signal.
16. The communications device of claim 14, wherein the received
indicator signal is a signal from which a channel quality estimate
is made; and wherein the antenna mode selection module selects the
dual polarized mode of operation when the channel quality estimate
indicates a first channel quality and selects the single polarized
mode of operation when the channel quality estimate indicates a
second channel quality which is lower than said first channel
quality.
17. The communications device of claim 16, further comprising: an
antenna mode indicator signal generation module for generating a
signal indicating the selected antenna mode of operation; and an
antenna mode indicator signal transmission control module for
controlling transmission of said antenna mode indicator signal.
18. A communications device comprising: a first antenna element
means for exchanging signals in a first polarization having first
polarization direction; a second antenna element means for
exchanging signals in a second polarization having a second
polarization direction, the second polarization direction being
different from the first polarization direction by at least 45
degrees; a first signal processing means for processing the signals
exchanged through the first antenna element means; and a second
signal processing means for processing the signals exchanged
through the second antenna element means.
19. The communications device of claim 18, wherein the first signal
processing means and the second signal processing means are for
recovering data from a first received signal and a second received
signal, the first received signal having a frequency that is the
same as the frequency of the second received signal, and the first
received signal having the first polarization different from the
second polarization of the second received signal.
20. The communication device of claim 18, wherein the first signal
processing means and the second signal processing means are for
generating a first transmission signal and a second transmission
signal, the first transmission signal having a frequency that is
the same as the frequency of the second transmission signal, and
the first transmission signal having the first polarization
different from the second polarization of the second transmission
signal.
21. The communications device of claim 18, further comprising: a
third antenna element means for exchanging signals in the first
polarization; an antenna switching means for coupling the second
antenna element means and the third antenna element means to the
second signal processing module means, the antenna switching means
for selectively passing signals between the second processing means
and one of the second antenna element means and the third antenna
element means at any given time.
22. The communications device of claim 21, further comprising: a
channel quality determination means for generating channel quality
indicators from received signals, the channel quality indicators
including a signal to noise ratio value.
23. The communications device of claim 22, further comprising: a
channel quality information transmission control means for
controlling transmission of channel quality information including
the signal to noise ratio value and rank information for a channel
matrix between transmitter antennas used to transmit to the
communications device and receive antennas included in the
communications device having a polarization which is the same as
the transmitter antennas.
24. The communications device of claim 23, further comprising: an
antenna mode indicator signal detection means for detecting receipt
of an antenna mode indicator signal and for recovering information
indicating one of a dual polarized mode of operation and a single
polarized mode of operation.
25. The communications device of claim 22, further comprising: an
antenna mode selection means for selecting between a dual polarized
mode of operation and a single polarized mode of operation as a
function of the generated channel quality indicators.
26. The communications device of claim 25, further comprising: an
antenna mode indicator signal generation means for generating a
signal indicating the selected antenna mode of operation; and an
antenna mode indicator signal transmission control means for
controlling transmission of the antenna mode indicator signal.
27. The communications device of claim 22, wherein the antenna
switching means is configured to couple the second antenna element
means to the second signal processing means when the dual polarized
mode of operation is selected; and wherein the antenna switching
means is configured to couple the third antenna element means to
the second signal processing means when the single polarized mode
of operation is selected.
28. The communications device of claim 27, wherein the first
polarization direction is a vertical direction; and wherein the
second polarization direction is a horizontal direction.
29. The communications device of claim 18, further comprising: an
antenna mode selection means for selecting between a dual polarized
mode of operation and a single polarized mode of operation as a
function of received channel quality information; wherein the first
received signal and the second received signal are received through
the first antenna element means and the second antenna element
means when the dual polarized mode of operation is selected; and
wherein the first received signal and the second received signal
are received through the first antenna element means and the third
antenna element means when the single polarized mode of operation
is selected.
30. The communications device of claim 19, further comprising: an
antenna mode selection means for selecting between a dual polarized
mode of operation and a single polarized mode of operation as a
function of received channel quality information; wherein the first
transmission signal and the second transmission signal are
transmitted through the first antenna element means and the second
antenna element means when the dual polarized mode of operation is
selected; and wherein the first transmission signal and the second
transmission signal are transmitted through the first antenna
element means and the third antenna element means when the single
polarized mode of operation is selected.
31. The communications device of claim 19, wherein the
communications device is a transceiver, the communications device
further comprising: a transmitter/receiver mode control means for
controlling whether the communications device operates in a
transmit or receive mode of operation; and an antenna mode
selection means for selecting between a dual polarized mode of
operation and a single polarized mode of operation as a function of
a received indicator signal, wherein the antenna mode selection
means selects the dual polarized or single polarized mode of
operation based on the antenna mode indicator signal.
32. The communications device of claim 31, wherein the received
indicator signal is an antenna mode indicator signal.
33. The communications device of claim 31, wherein the received
indicator signal is a signal from which a channel quality estimate
is made; and wherein the antenna mode selection means selects the
dual polarized mode of operation when the channel quality estimate
indicates a first channel quality and selects the single polarized
mode of operation when the channel quality estimate indicates a
second channel quality which is lower than said first channel
quality.
34. The communications device of claim 33, further comprising: an
antenna mode indicator signal generation means for generating a
signal indicating the selected antenna mode of operation; and an
antenna mode indicator signal transmission control means for
controlling transmission of said antenna mode indicator signal.
Description
RELATED PATENT APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/032,454, entitled "METHODS AND APPARATUS
FOR USING MULTIPLE ANTENNAS HAVING DIFFERENT POLARIZATION",
Attorney Docket No. 070653, filed on Feb. 15, 2008, and
incorporated by reference in its entirety, herein.
FIELD
[0002] Various embodiments relate to wireless communications
devices, and more particularly, to methods and apparatus for
supporting dual and single polarization modes of operation in a
communications device.
BACKGROUND
[0003] The importance of using multiple antennas in multiple input
multiple output systems (MIMO) has been well understood. However,
much focus has been on using vertically polarized spatial antenna
array configurations.
[0004] Although spatial MIMO configurations have proven to be quite
effective, a number of problems still exist with such spatial
configurations. Most cellular propagation scenarios are
characterized by the existence of a strong dominant path causing
the spatial MIMO channel matrix to be rank deficient. Furthermore,
an inter element spacing requirement in spatial configurations
restricts the amount of permissible scaling down of a mobile
device, as one attempts to make a mobile device more and more
compact. Also, the interference resulting due to spatial antenna
arrays is much higher as compared with the interference between a
vertically polarized antenna and a horizontally polarized antenna.
Thus, for one or more of the above reasons, there can be advantages
in implementing an approach of using differently polarized antennas
over an approach of using spatial antenna array with a single
polarized antenna direction.
[0005] In view of the above discussion, it would be desirable if
improved methods and apparatus could be developed to improve user
experience in propagation scenarios characterized by a strong
dominant path, without compromising compactness and size of mobile
devices and without adding too much complexity to the current
system in use,
SUMMARY
[0006] Methods and apparatus for operating a communications device
capable of using single and dual polarization modes of antenna
operation are described.
[0007] Polarization diversity refers to the signaling strategy
whereby, information signals are transmitted and received
simultaneously on orthogonally polarized waves. In one exemplary
embodiment, a communications device employs dual polarized antennas
with collocated orthogonally polarized elements to yield compact
array configuration at the base station and/or at the mobile
station. Such a dual polarized antenna configuration provides at
least two degrees of freedom, even in propagation scenarios with a
strong dominant component. Also, it achieves tow correlation
between the elements of a MIMO channel matrix, while having a
compact array configuration.
[0008] Various embodiments are directed to a wireless
communications device in which, an antenna selection technique has
been adopted so that a judiciously chosen subset of antennas are
used by the device. The device switches between a dual polarized
mode of operation and a single polarized mode of operation. In some
embodiments, the selection between the dual polarized mode of
operation and the single polarized mode of operation is based on a
channel quality estimate, e.g. an SNR measurement, rank information
and/or a channel quality indicator value, or is in response to an
antenna mode indicator signal. In some, but not necessarily all
embodiments, when dual polarization mode is used different data is
communicated over each of the differently polarized antennas, e.g.,
with each polarization operating as a different communications pipe
through which data may be sent. In the single polarized mode of
operation, in some embodiments, the same data is transmitted using
two or more antenna elements having the same polarization. In the
single polarized mode of operation, in some embodiments, the
antenna elements operate together to support a data pipe
corresponding to a single polarization between the sending and
receiving devices. Alternatively, in some embodiments, two
different data streams are communicated in the single polarized
mode of operation from the different antennas, when the channel
matrix is rank 2, indicating that the two streams can be separated
at the receiver.
[0009] A communications device, e.g., an access node such as a base
station or a wireless terminal such as a mobile node, in accordance
with various embodiments, comprises: a first antenna element
polarized in a first direction; a second antenna element polarized
in a second direction, said first and second directions being
different by at least 45 degrees; a first signal processing module
coupled to said first antenna element; and a second signal
processing module coupled to said second antenna element. An
exemplary method of operating a wireless communications device,
e.g., an access node or wireless terminal, in accordance with
various embodiments comprises: operating during a first period of
time in a dual polarized mode of antenna operation; and operating
during a second period of time in a single polarized mode of
antenna operation, said first and second periods of time being
different.
[0010] While various embodiments have been discussed in the summary
above, it should be appreciated that not necessarily all
embodiments include the same features and some of the features
described above are not necessary but can be desirable in some
embodiments. Numerous additional features, embodiments and benefits
of various embodiments are discussed in the detailed description
which follows,
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 illustrates an exemplary communications device as
implemented in accordance with various embodiments.
[0012] FIG. 2 illustrates a flowchart showing the steps of an
exemplary method to operate a communications device in a selected
mode of operation in accordance with an embodiment.
[0013] FIG. 3 illustrates a flowchart showing the steps of an
exemplary method to operate a communications device in a selected
mode of operation in accordance with yet another embodiment.
[0014] FIG. 4 illustrates an exemplary memory which may be used in
the wireless communications device shown in FIG. 1.
[0015] FIG. 5 is a drawing of an exemplary communications system
including two wireless communications devices which support MIMO
operations and antenna switching, each device including two
antennas polarized in a vertical direction and an antenna polarized
in a horizontal direction.
[0016] FIG. 6 is a drawing illustrating 2.times.2 MIMO capacity
with spatial and dual polarized configurations.
[0017] FIG. 7 includes a drawing illustrating an exemplary sequence
of intervals including evaluation intervals and data intervals in
an exemplary timing structure in accordance with one exemplary
embodiment.
[0018] FIG. 8 includes a drawing illustrating another exemplary
sequence of intervals including evaluation intervals and data
intervals in an exemplary timing structure in accordance with one
exemplary embodiment.
DETAILED DESCRIPTION OF THE FIGURES
[0019] FIG. 1 illustrates an exemplary communications device 200 as
implemented in accordance with various exemplary embodiments.
Exemplary communications device 200 is, e.g., an access node such
as a base station or a wireless terminal such as a mobile node. A
wireless terminal is sometimes referred to as an access terminal or
an end node. The wireless communications device 200 includes a
first antenna 202, a second antenna 204, a third antenna 206, an
antenna switching module 208, a Receive/Transmit (Rx/Tx) switch
module 210, a first transmitter module 212, a first receiver module
214, a second transmitter module 218, a second receiver module 216,
an antenna mode selection module 224, a channel quality
determination module 234, e.g., a channel estimator module to
estimate channel quality, a combining module 236, a first symbol
recovery module 238, a second symbol recovery module 240, an input
device 242, an Input/Output WO) interface 244, an output device
246, a processor 250, a memory unit 248, a transmitter/receiver
control module 247, and an output signal module 249. The I/O
interface 244 is coupled to an input device 242, e.g., keypad,
microphone, camera, keyboard, mouse, etc., and output device 246,
e.g., display, speaker, etc., which can be used by a user to
interact with the communications device 200. In some embodiments,
multiple individual antennas are described as being used; it should
be appreciated that alternatively that a single antenna assembly
with multiple antenna elements may be used, instead of individual
distinct antennas. For example, a first antenna element polarized
in a first direction, a second antenna element polarized in the
second direction, and a third antenna element polarized in the
first direction, which are part of an antenna assembly, are used in
some embodiments.
[0020] Transmitter module 1 212 includes an encoder 215 and a
modulator 213. Encoder module 215 processes DT1 information, e.g.,
bits of information representing user data, control signals, etc.,
generating encoded bits which are used by modulator 213 to generate
symbols to be transmitted. Transmitter module 2 218 includes an
encoder 227 and a modulator 225. Encoder module 227 processes DT2
information, e.g., bits of information representing user data,
control signals, etc., generating encoded bits which are used by
modulator 225 to generate symbols to be transmitted. Receiver
module 1 214 includes a filter 217 and an analog to digital
converter 219. Filter 217 filters out undesired frequencies and
noise and then A/D converter 219 converts the filtered analog
signal to a digital signal. Receiver module 2 216 includes a filter
221 and an analog to digital converter 223. Filter 221 filters out
undesired frequencies and noise and then A/D converter 223 converts
the filtered analog signal to a digital signal.
[0021] I/O interface 244, processor 250, memory 248, output signal
module 249, and a transmitter/receiver control module 247 are
coupled together via a bus 252 via which the various elements may
interchange data and information. Memory 248 includes routines and
data/information. The processor 250, e.g., a CPU, executes the
routines and uses the data/information in memory 248 to control the
operation of the communications device 200 and implement methods,
e.g., the method of flowchart 100 of FIG. 2 or the method of
flowchart 300 of FIG. 3.
[0022] In some but not necessarily all embodiments, the
communications device 200 may have a channel quality indicator
(CQI) signal generation module 230 coupled to a channel quality
information transmission control module 232. In various
embodiments, the communications device includes an antenna mode
indicator signal generation module 220 coupled to an antenna mode
indicator signal transmission control module 222. In some
embodiments, the I/O interface 244 has a connection for coupling
the communications device 200 to other devices, e.g., by a wired or
fiber optic connection.
[0023] In various embodiments, the antenna mode selection module
234 includes one or more of an antenna mode indicator signal
detection module 226 and a channel based antenna mode decision
module 228. Antenna mode indicator signal detection module 226 is
for detecting receipt of an antenna mode indicator signal and for
recovering information indicating one of a dual polarized mode of
operation and a single polarized mode of operation.
[0024] The first antenna 202 which is polarized in a first
direction, e.g. the vertical direction, is coupled to the antenna
switching module 208. The second antenna 204 which is polarized in
a second direction, e.g. the horizontal direction, is also coupled
to the antenna switching module 208. Third antenna 206 which is
polarized in the first direction is also coupled to the antenna
switching module 208. Switching between the second antenna 204 and
the third antenna 206 is performed by the antenna switching module
208 as a function of a switching control signal from the antenna
mode selection module 224. Thus, antenna switching module 208 is
used to couple the second and third antennas (204, 206) to a signal
processing module, e.g., receiver module 2 216 or transmitter
module 2 218, and the antenna switching module 208 selectively
passes signals between one of: i) the second antenna 204 and ii)
the third antenna 206 and the signal processing module at any given
time.
[0025] The first and second directions are different from each
other by at least 45 degrees some embodiments, the first and second
directions are substantially orthogonal. In various embodiments,
the first direction is a vertical direction and the second
direction is a horizontal direction.
[0026] The Rx/Tx switch module 210 couples the antenna switching
module to either the transmitter modules (212, 218) or to the
receiver modules (214, 216) as a function of a control signal from
the transmitter/receiver control module 247. With regard to the
first antenna 202, the antenna switching module 208 and the RX/TX
switch module 210, in combination, couple the first antenna 202 to
either transmitter module 1 212 or receiver module 1 214.
[0027] The second antenna 204 or third antenna 206, whichever at a
given time is selected via antenna switching module 208, is
coupled, via RX/TX switch module 210 to one of receiver module 2
216 or transmitter module 2 218 as a function of the control signal
from transmitter/receiver control module 247.
[0028] Consider that the first antenna 202 is coupled to receiver
module 1 214, which is a signal processing module, and that the
second antenna 204 is coupled to receiver module 2 216, which is
another signal processing module, the receiver modules (214, 216)
are used for recovering data from first and second received signals
having the same frequency but different polarization.
Alternatively, consider that the first antenna 202 is coupled to
the transmitter module 1 212, a signal processing module, and that
the second antenna 204, is coupled to transmitter module 2 218,
another signal processing module, the transmitter modules (212,
218) are used for generating first and second signals having the
same frequency to be transmitted with different polarizations.
[0029] For some embodiments, the communications device 200 sends
pilot signals via the first polarization direction antennas,
antenna 202 and 206, e.g., the vertical polarization antennas, aver
the air link using the first and second transmitter modules 212 and
218, respectively. For example, in one such embodiment,
communications device 200 is an access node such as abase station
which sends pilots signals to a wireless terminal such as mobile
node to facilitate channel estimation upon which an initial
selection between a dual and single mode of polarization operation
is based various embodiments, the access node transmits pilot
signals over a selected antenna irrespective of the mode of
operation. For example, when in single polarization mode device
200, e.g., an access node, sends pilot signals over first antenna
202 and third antenna 206, while in dual polarization mode, the
communications device 200, e.g., an access node, sends pilot
signals over the first antenna 202 and second antenna 204. Such
transmitted pilot signals, can be, and in some embodiments, are
utilized in determining whether or not to switch between single and
dual polarization modes of operation.
[0030] Now consider an exemplary embodiment where the
communications device 200 is, e.g., a wireless terminal such as a
mobile node, sometimes referred to as an access terminal. For some
embodiments, the receivers (214, 216) feed the received signals,
e.g., received signals including received pilot signals, to the
channel quality determination module 234, e.g., a channel estimator
module, to estimate the channel quality. Channel quality
determination module 234 generates channel quality indicators from
received signals, and the channel quality indicators include a
signal to noise ratio value. Other channel quality indicators
include rank information for a channel matrix between transmitter
antennas used to transmit to device 200 and receive antennas in
device 200 having a polarization which is the same as the
transmitter antennas. Other channel quality indicators include
additional signal to noise ratios, e.g., a separate signal to noise
rate for each transmit antenna/receive antenna pair. In some
embodiments, channel quality estimation operations performed by
channel quality determination module, e.g., channel estimator
module 234, includes determining a plurality of signal to noise
ratios (SNRs), computing rank information corresponding to a
communications channel matrix, and/or determining other channel
estimation information.
[0031] Channel quality determination module 234, e.g., an estimator
module, includes an SNR sub-module 251 and a rank sub-module 253.
SNR sub-module 251, of channel estimator module 234, performs SNR
measurements, e.g., corresponding to individual feeds from a
receiver module corresponding to individual communications
channels. Rank sub-module 253 of channel estimator module 234,
determines rank information, e.g., a rank value, for a
communications channel matrix corresponding to signals from both
receiver module 1 214 and receiver module 2 216.
[0032] The channel quality determination module 234 is coupled to
receiver modules (214, 216), via which module 234 receives input
signals for evaluation. In some embodiments, the channel
determination module 234 is also coupled to the channel based
antenna mode decision module 228 of the antenna mode selection
module 224. In some such embodiments, the channel based antenna
mode decision module 228 uses channel estimation information, e.g.,
SNR and/or rank information, from channel estimator module 234 and
decides whether communications device 200 is to be operating in a
single polarization mode of operation or a dual polarization mode
of operation. A decision signal from decision module 228 is fed to
antenna mode indicator signal generator module 220, which generates
an antenna mode indicator signal to be conveyed to the device
communicating with device 200. The antenna mode indicator signal
generation module 220 is also coupled to antenna mode indicator
signal transmission control module 222 which generates a
transmission indicator control signal used to control transmitter
module 1 212 and/or transmitter module 2 218 to transmit the
generated antenna mode indicator signal.
[0033] The antenna mode selection module 224 includes one or more
of antenna mode indicator signal detection module 226 and a channel
based antenna mode decision module 228. The antenna mode selection
module 224 makes the decision as to which mode the device will
operate in, i.e. either (i) the single polarized mode of antenna
operation where only first direction polarized antennas, e.g.,
vertically polarized antennas, are used to send and/or receive
signals and data or (ii) the dual polarized mode of antenna
operation where both, a first and second direction polarized
antennas, e.g., a horizontally polarized antenna and a vertically
polarized antenna, are used to send and/or receive signals and
data. When the dual polarized mode of operation is selected by
module 224, the antenna switching module 208 is controlled to
couple the second antenna 204 to a second signal processing module,
e,g., receiver module 2 216 or transmitter module 2 218. When the
single polarized mode of operation is selected by module 224, the
antenna switching module 208 is controlled to couple the third
antenna 206 to a second signal processing module, e.g., receiver
module 2 216 or transmitter module 2 218. Thus in dual polarized
mode signals over the first and second antennas (202, 204) are used
to support communications, while in the single polarized mode
signals over the first and third antennas (202, 206) are used to
support communications.
[0034] In some embodiments the decision of antenna mode of
operation is made by the antenna mode selection module 224 based on
the channel quality information as provided by the channel
estimator in the form of SNRs and/or rank. In such embodiments, the
channel based antenna mode decision module 228 is responsible for
the decision making. In some embodiments, the antenna mode
selection module 224 selects the dual polarized mode of operation
when the channel quality estimate indicates a first channel quality
and selects the single polarized mode of operation when the channel
quality estimate indicates a second quality which is lower than the
first quality.
[0035] In one such embodiment, the channel based antenna mode
decision module is coupled to an antenna mode indicator signal
generation module 220. The antenna mode indicator signal generation
module 220 generates an indicator signal indicating the selected
antenna mode of operation, the selection being performed by device
200. The generated indicator signal is used to convey the mode
decision of decision module 228. The generated indicator signal is
input to the output signal module 249. The output signal module 249
generates data for transmission over receiver 1 (DT1) and data for
transmission over receiver 2 (DT2), which is input to the
transmitter modules (212, 218), respectively. As an example,
consider the case where communications device 200 is a wireless
terminal, and device 200 makes antenna mode selection decisions as
a function of channel estimation information and communicates its
decision via an indicator signal to an access node. The indicator
signal indicates one of dual polarized antenna mode and single
polarized antenna mode.
[0036] In some embodiments, the channel quality determination
module 234, e.g., an estimator module, is coupled to a channel
quality indicator (CQI) signal generation module 230, which is
coupled to a channel quality information signal transmission
control module 232. Channel quality &termination module 234
estimates channel quality obtaining SNR information, rank
information, and/or information based on SNR information and/or
rank information. Such information is forwarded to the CQI signal
generation module 230 which generates a CQI indicator signal. The
generated CQI indicator signal is an input to output module 249
which generate DT1 information and DT2 information, which is an
input to transmitter modules (212, 218), respectively. CQI signal
transmission control module 232 generates a CQI transmission
control signal which is used to control the transmitter modules
(212, 218) to transmit the generated CQI control signal. Thus
channel quality information transmission control module 232
controls transmission of channel quality information, said channel
quality information including a signal to noise ratio value and one
of: i) rank information for a channel matrix between transmitter
antenna used to transmit to device 200 and receive antenna included
in device 200 having a polarization which is the same as the
transmitter antennas and ii) additional signal to noise ratio
information. As an example, consider the case where communications
device 200 is a wireless terminal, and device 200 estimates channel
quality information, generates a channel quality indicator signal
which it communicates to an access node, e.g., a base station. The
access node uses the received channel quality indicator signal from
communications device 200, e.g., wireless terminal 200, and the
access node makes the decision as to the antenna mode of operation
to be used by the communications device 200.
[0037] In some embodiments the antenna mode decision is made by the
antenna mode selection module 224 based on die detection of an
antenna mode indicator signal, as detected by the antenna mode
indicator signal detection module 226. For example, consider an
example, where communications device 200 does not make the decision
as to the antenna mode of operation, but rather implements a
decision made at a device which is remote to itself. For example,
consider that communications device 200 is a wireless terminal and
the device which makes the antenna mode decision is abase station,
which transmits an antenna mode indicator signal to device 200. The
signal is received via receiver modules (214, 216), subsequently
processed by modules (236, 238 and 241) and detected by detection
module 226 of antenna mode selection module 224 which generates and
sends a switching control signal to antenna switching module 208 to
implement the mode decision of the base station.
[0038] Alternatively, in another example, communications device 200
is a base station, and the protocol used in the communications
system is such that the wireless terminal makes the decision as to
the antenna mode of operation and communicates the decision to the
base station. Then, antenna mode indicator signal detection module
226 detects a wireless terminal antenna mode decision.
[0039] The Rx/Tx switch module 210, under control of
transmitter/receiver control module 210 is used to select between
the transmitter and receiver modules based on what operation is
needed to be performed by the device 200 i.e. either transmission
or reception. The Rx/Tx switch module 210 will perform the
switching operation and will select between the receiver modules
and the transmitter modules based on the control signal supplied to
the switch by the Rx/Tx switching control module 247.
[0040] The first receiver module 214, processes the received signal
from the first antenna 202 by operations including filtering the
received signal for noise and interference using the filter 217.
The filtered signal is then fed to A/D converter 219, in order to
convert analog data into digital, for further data processing in
digital domain. The second receiver module 216, processes the
received signal from the second antenna 204 or third antenna 206 by
operations including filtering the received signal for noise and
interference using filter 221. The filtered signal 221 is then fed
to A/D converter 223, in order to convert analog data into digital,
for further data processing in digital domain. The digital output
from, the first receiver module 214 and the second receiver module
216 is fed to the combining module 236 where the output from the
two receivers is combined and then data streams are separated out
and fed to the symbol recovery modules 238 and 240. Then data
stream 1 (DS1) and data stream 2 (DS2) can be recovered from the
symbol recovery modules (238, 240), respectively. In some
embodiments, there is only a single data stream, in which case only
on of the symbol recovery modules should be used.
[0041] Memory 248 which may be implemented as an exemplary memory
unit 400 of FIG. 4, includes routines and data/information and will
be discussed in detail further with respect to FIG. 4. The
processor 250, e.g., a CPU, executes the routines and uses the
data/information in the memory 248 to control the operation of the
communications device 200 and implement methods, e.g., the method
of flowchart 100 of FIG. 2 and/or the method of flowchart 300 of
FIG. 3.
[0042] FIG. 2 illustrates a flowchart 100 showing the steps of an
exemplary method to operate a communications device, e.g. the
communications device 200 of FIG. 1. The communications device
performing the method of flowchart 100 is, e.g., a wireless
terminal such as mobile node. The communications device may be
operated in either a single polarized mode of antenna operation or
dual polarized mode of antenna operation. The exemplary method
starts in step 102, where initialization is performed, and proceeds
from start step 102 to step 104. In step 104, current mode of
operation is set to the single polarized mode of antenna operation,
e.g., vertical mode of antenna operation. In the single polarized
mode of antenna operation, the antennas being used for
communication are polarized in the same direction, e.g., two
antenna used for communications, e.g., a first antenna and a third
antenna, are vertically polarized. The operation proceeds from step
104 to step 106.
[0043] In step 106, the communication device is operated to receive
pilot signals from a second device, e.g. abuse station. White
receiving pilots is shown as a separate step, step 106, the receipt
of pilots may occur as part of the data mode of operation, e.g., as
part of or in addition to sub-stop 140 and/or sub-step 150. Step
106 may also include switching of the mode of operation, e.g., in
order that pilots may be received in the mode of operation which is
different than the previous mode of operation used for
communicating data signals. The operation proceeds from step 106 to
step 108. In step 108, communications device estimates channel
quality, e.g., obtaining SNRs. For example, SNR sub-module 251 of
channel quality determination module 234, e.g., a channel estimator
module, of FIG. 1, determines SNRs corresponding to different
channels. In step 108, the estimate of channel quality is based on
one or more pilots received in a single polarized mode of
operation. Optionally, pilots used during a dual mode of operation
may be used to generate another one of multiple channel quality
estimates that are generated in step 108 in some, but not
necessarily all embodiments. Operation proceeds from step 108 to
steps 110 and 112.
[0044] In step 110 the communications device generates rank
information for a channel matrix between transmitter and receiver
antennas. For example, rank sub-module 253 of channel quality
termination module 234 computes a rank value for the channel
matrix. In sub-step 112 the communications device generates a
channel quality indicator value. For example, CQI signal generation
module 230 of FIG. 1 generates a channel quality indicator signal.
Operation proceeds from steps 110 and 112 to step 114.
[0045] In step 114, the communications device transmits the channel
quality information, e.g., SNR information, rank information,
and/or a channel quality indicator (CQI) value. Operation proceeds
from step 114 to step 116.
[0046] In step 116 the communications device determines, e.g.,
based on an implemented protocol, whether or not a remote device
gets to decide the antenna mode for the communications device
implementing the method of flowchart 100. If a remote device does
not get to decide the antenna mode for the communications device
then operation proceeds from step 116 to step 118; otherwise,
operation proceeds from step 116 to step 120.
[0047] In step 118, the communications device selects the antenna
mode based on channel quality information, e.g., SNR information,
rank information, and/or channel quality indicator information. In
some embodiments, the communications device selects between the
dual polarized mode of antenna operation and the single polarized
mode of antenna operation based on both the channel quality
estimate and generated rank information. Operation proceeds from
step 118 to step 122, in which the communications device generates
an antenna mode signal, and then in step 124 the communications
device transmits the generated antenna mode signal over an airlink,
e.g., to the base station which transmitted the received pilot
signals of step 106. Operation proceeds from step 124 to step
126.
[0048] Returning to step 120, in step 120 the communications device
is operated to receive an antenna mode indicator signal. Then, in
step 128 the communications device selects the antenna mode for the
communications device based on the received antenna mode indicator
signal. Operation proceeds from step 128 to step 126.
[0049] In some embodiments, an alternative implementation is used
in which the communications device monitors for an antenna mode
indicator signal from a remote device. If the monitoring does not
detect an antenna mode indicator signal from the remote device,
then the communications device determines the antenna mode based on
estimated channel quality information. However, if the
communications device detects an antenna mode indicator signal,
then the mode indicated by the received antenna mode indicator
signal is the selected antenna mode. Thus, in such an embodiment,
the communications device's default mechanism for selecting antenna
mode is its own estimation of channel quality information; however,
received mode indicator signals can, and sometimes do, serve as an
override or higher priority mechanism used to select antenna
mode.
[0050] Returning to step 126, step 126 is a decision making step
and in step 126 the communications device determines if the
selected mode of operation, from step 118 or step 128, is the
current mode in which the communications device is operating. If it
is determined that the selected mode happens to be the current
mode, the operation proceeds from step 126 to step 132. If the
selected mode is not same as current mode of operation then
operation proceeds from step 126 to step 130.
[0051] In step 130, the communications device switches from its
present current mode of operation to selected mode of operation,
and the operation proceeds to step 132. Thus in step 130, the
current mode is updated: current mode (updated)=selected mode (of
step 118 or 128). In various embodiments, switching the current
mode to the selected mode includes commanding an antenna switching
module, e.g., antenna switching module 208 of FIG. 1, to change
switch position. In some embodiments, switching is performed at
specific points in time within a predetermined timing structure at
which the wireless communications device is permitted to switch
between the dual polarized mode of operation and the single
polarized mode of operation.
[0052] Step 132 is also a decision making step and in this step the
communications device determines if the current triode of operation
is a dual polarized mode of antenna operation. Thus in step 132 the
communications device proceeds differently depending upon whether
the current triode of operation is a dual polarized mode of
operation or a single polarized mode of operation. If the answer to
the decision making step 132 is yes, then operation proceeds from
step 132 to step 134. However, if the answer to the decision making
step 132 is no, then operation proceeds from step 132 to step
136.
[0053] In step 134, the communications device is operated in dual
polarized mode of antenna operation. In this mode of operation one
of the antennas used, e.g. first antenna 202 of FIG. 1, is
polarized in the first polarization direction, e.g., the vertical
direction, and another antenna used, e.g. second antenna 204 of
FIG. 1, is polarized in the second polarization direction, e.g.,
the horizontal direction. Step 134 includes sub-steps 138, 140, 142
and 144. In sub-step 138, the communications device selects between
transmit and receive mode. If the selection of decision step 138 is
receive mode then operation proceeds from sub-step 138 to sub-step
140; however, if the decision of sub-step 138 is to transmit, then
operation proceeds from sub-step 138 to sub-step 142. In sub-step
138, the communications device recovers data from signals output
from the first and second antennas, which are polarized at more
than 75 degrees with respect to each other. In sub-step 142, the
communications device transmits data from the first and second
antennas. Operation proceeds from sub-step 140 or 142 to sub-step
144. In sub-step 144 the communications device decides whether it
should loop back to make another receive/transmit decision in the
dual polarized mode or whether it should exit and go back and
reconsider its mode of operation. If it decides in sub-step 144 to
exit, then operation proceeds from step 134 to step 106. However,
if the decision in sub-step 144 is not to exit, then operation
proceeds from sub-step 144 to sub-step 138. In some embodiments,
the exit decision of sub-step 144 is based upon time. In some such
embodiments, the allowable rate of mode switching between dual
polarized antenna mode and single polarized antenna mode is less
than the allowable rate of switching between receive and transmit
modes of operation.
[0054] Returning to step 136, in step 136, the communications
device is operated in the single polarized mode of antenna
operation. In this mode of operation, multiple antennas being used
for communication are polarized in same direction, e.g. both the
first antenna 202 of FIG. 1 which is used, is polarized in the
first, e.g., vertical, direction and another antenna, e.g. third
antenna 206 of FIG. 1, is also polarized in the same first, e.g.,
vertical, direction, without using other antennas which are
polarized in a different direction. For example, the second antenna
204 of FIG. 1 which is polarized in a second direction, e.g., the
horizontal direction, is not used in the single polarized mode of
operation.
[0055] Step 136 includes sub-steps 146, 148, 150 and 152. In
sub-step 146, the communications device selects between transmit
and receive modes. If the selection of decision step 138 is receive
mode then operation proceeds front sub-step 146 to sub-step 150.
However, if the decision of sub-step 146 is to transmit, then
operation proceeds from sub-step 146 to sub-step 148. In sub-step
150, the communications device recovers data from signals output
from multiple antennas polarized in the first direction without
using the output of an antenna polarized in a different direction.
For example, with regard to FIG. 1, communications device 200
recovers data received via first and third antenna (202, 206),
respectively, but does not use the output of second antenna 204. In
sub-step 148, the communications device transmits data from
multiple antennas polarized in the first direction without
transmitting data on an antenna polarized in a different direction.
For example, with regard to device 200 of FIG. 1, signals are
transmitted via first and third antennas (202, 206), polarized in
the first, e.g., vertical direction, without transmitting via the
second antenna 204 which is polarized in the second direction,
e.g., horizontal direction. Operation proceeds from sub-step 148 or
150 to sub-step 152. In sub-step 152 the communications device
decides whether it should loop back to make another
receive/transmit decision in the single polarized mode or whether
it should exit and go back and reconsider its mode of antenna
operation. If it decides in sub-step 152 to exit, then operation
proceeds from step 126 to step 106. However, if the decision in
sub-step 152 is not to exit, then operation proceeds from sub-step
152 to sub-step 146. In some embodiments, the exit decision of
sub-step 152 is based upon time. In some such embodiments, the
allowable rate of mode switching between dual polarized antenna
mode and single polarized antenna mode is less than the allowable
rate of switching between receive and transmit modes of
operation.
[0056] FIG. 3 illustrates a flowchart 300 showing the steps of an
exemplary method to operate a communications device, e.g., the
communications device 200 of FIG. 1. The communications device
performing the method of flowchart 300 is, e.g., an access node
such as a base station. The communications device may be operated
in either a single polarized mode of antenna operation or dual
polarized mode of antenna operation. The exemplary method starts in
step 302, where initialization is performed, and proceeds from
start step 302 to step 304. In step 304, current mode of operation
is set to the single polarized mode of antenna operation, e.g.,
vertical mode of antenna operation. In the single polarized mode of
antenna operation, the antennas being used for communication are
polarized in the same direction, e.g., two antenna used for
communications, e.g., a first antenna and a third antenna, are
vertically polarized. The operation proceeds from step 304 to step
306.
[0057] In step 306, the communication device is operated to
transmit pilot signals to a second device, e.g. to a wireless
terminal using the communications device, e.g., base station, as a
point of attachment. The operation proceeds from step 306 to step
308. In step 308, communications device receives channel quality
information, e.g., SNR information, rank information, and/or a
channel quality indicator value. For example, multiple SNRs
corresponding to different channels are received. As another
example, rank information for a channel matrix between transmitter
and receiver antennas is received. As still another example, a
channel quality indicator value is received. Operation proceeds
from step 308 to step 310.
[0058] In step 310 the communications device determines, e.g.,
based on an implemented protocol, whether or not a remote device
gets to decide the antenna mode for the communications device
implementing the method of flowchart 300. If a remote device does
not get to decide the antenna mode for the communications device
then operation proceeds from step 310 to step 312; otherwise
operation proceeds from step 310 to step 314.
[0059] In step 312, the communications device selects the antenna
mode based on channel quality information, e.g., SNR information,
rank information, and/or channel quality indicator information. In
some embodiments, the communications device makes a selection
between the dual polarized mode of antenna operation and the single
polarized mode of antenna operation based on both a channel quality
estimate and rank information. Operation proceeds from step 312 to
step 316, in which the communications device generates an antenna
mode signal, and then in step 318 the communications device
transmits the generated antenna mode signal over an airlink, e.g.,
to the wireless terminal which transmitted the received channel
quality information of step 308. Operation proceeds from step 318
to step 322.
[0060] Returning to step 314, in step 314 the communications device
is operated to receive an antenna mode indicator signal. Then, in
step 320 the communications device selects the antenna mode for the
communications device based on the received antenna mode indicator
signal. Operation proceeds from step 320 to step 322.
[0061] In some embodiments, an alternative implementation is used
in which the communications device monitors for an antenna mode
indicator signal from a remote device. If the monitoring does not
detect an antenna mode indicator signal from the remote device, hen
the communications device determines the antenna mode based on
received channel quality information. However, if the
communications device detects an antenna mode indicator signal,
then the mode indicated by the received antenna mode indicator
signal is the selected antenna mode. Thus, in such an embodiment,
the communications device's default mechanism for selecting antenna
mode is its own determination based on received channel quality
information; however, received mode indicator signals can, and
sometimes do, serve as an override or higher priority mechanism
used to select antenna mode.
[0062] Returning to step 322, step 322 is a decision making step
and in step 322 the communications device determines if the
selected mode of operation, from step 312 or step 320, is the
current mode in which the communications device is operating. If it
is determined that the selected mode happens to be the current
mode, the operation proceeds from step 322 to step 326. If the
selected mode is not same as current mode of operation then
operation proceeds from step 322 to step 324.
[0063] In step 324, the communications device switches from its
present current mode of operation to selected mode of operation,
and the operation proceeds to step 326. Thus in step 324, the
current mode is updated: current mode (updated)=selected mode (of
step 312 or 320). In various embodiments, switching the current
mode to the selected mode includes commanding an antenna switching
module, e.g., antenna switching module 208 of FIG. 1, to change
switch position. In some embodiments, switching is performed at
specific points in time within a predetermined timing structure at
which the wireless communications device is permitted to switch
between the dual polarized mode of operation and the single
polarized mode of operation.
[0064] Step 326 is also a decision making step and in this step the
communications device determines if the current mode of operation
is a dual polarized mode of antenna operation. Thus in step 326 the
communications device proceeds differently depending upon whether
the current mode of operation is a dual polarized mode of operation
or a single polarized mode of operation. If the answer to the
decision making step 326 is yes, then operation proceeds from step
326 to step 328. However, if the answer to the decision making step
326 is no, then operation proceeds from step 326 to step 330.
[0065] In step 328, the communications device is operated in dual
polarized mode of antenna operation. In this mode of operation one
of the antennas used, e.g. first antenna 202 of FIG. 1, is
polarized in the first polarization direction, e.g., the vertical
direction, and another antenna used, e.g. second antenna 204 of
FIG. 1, is polarized in the second polarization direction, e.g.,
the horizontal direction. Step 328 includes sub-steps 332, 334, 336
and 338. In sub-step 332, the communications device selects between
transmit and receive mode. If the selection of decision step 332 is
receive mode then operation proceeds from sub-step 332 to sub-step
334; however, if the decision of sub-step 332 is to transmit, then
operation proceeds from sub-step 332 to sub-step 336. In sub-step
334, the communications device recovers data from signals output
from the first and second antennas, which are polarized at more
than 75 degrees with respect to each other. In sub-step 336, the
communications device transmits data from the first and second
antennas. Operation proceeds from sub-step 334 or 336 to sub-step
338. In sub-step 338 the communications device decides whether it
should loop back to make another receive/transmit decision in the
dual polarized mode or whether it should exit and go back and
reconsider its mode of operation. If it decides in sub-step 338 to
exit, then operation proceeds from step 328 to step 306. However,
if the decision in sub-step 338 is not to exit, then operation
proceeds from sub-step 338 to sub-step 332. In some embodiments,
the exit decision of sub-step 338 is based upon time. In some such
embodiments, the allowable rate of mode switching between dual
polarized antenna mode and single polarized antenna mode is less
than the allowable rate of switching between receive and transmit
modes of operation.
[0066] Returning to step 330, in step 330, the communications
device is operated in the single polarized mode of antenna
operation. In this mode of operation, multiple antennas being used
for communication are polarized in same direction, e.g. both the
first antenna 202 of FIG. 1 which is used, is polarized in the
first, e.g., vertical, direction and another antenna, e.g. third
antenna 206 of FIG. 1, is also polarized in the same first, e,g.,
vertical, direction, without using other antennas which are
polarized in a different direction. For example, the second antenna
204 of FIG. 1 which is polarized in a second direction, e.g., the
horizontal direction, is not used in the single polarized mode of
operation.
[0067] Step 330 includes sub-steps 340, 342, 344 and 346. In
sub-step 340, the communications device selects between transmit
and receive mode. If the selection of decision step 340 is receive
mode then operation proceeds from sub-step 340 to sub-step 344;
however, if the decision of sub-step 340 is to transmit, then
operation proceeds from sub-step 340 to sub-step 342. In sub-step
344, the communications device recovers data from signals output
from multiple antennas polarized in the first direction without
using the output of an antenna polarized in a different direction.
For example, with regard to FIG. 1, communications device 200
recovers data received via first and third antenna (202, 206),
respectively, but does not use the output of second antenna 204. In
sub-step 342, the communications device transmits data from
multiple antennas polarized in the first direction without
transmitting data on an antenna polarized in a different direction.
For example, with regard to device 200 of FIG. 1, signals are
transmitted via first and third antennas (202, 206), polarized in
the first, e.g., vertical direction, without transmitting via the
second antenna. 204 which is polarized in the second direction,
e.g., horizontal direction. Operation proceeds from sub-step 342 or
344 to sub-step 346. In sub-step 346 the communications device
decides whether it should loop back to make another
receive/transmit decision in the single polarized mode or whether
it should exit and go back and reconsider its mode of antenna
operation. If it decides in sub-step 346 to exit, then operation
proceeds from step 330 to step 306. However, if the decision in
sub-step 346 is not to exit, then operation proceeds from sub-step
346 to sub-step 340. In some embodiments, the exit decision of
sub-step 346 is based upon time. In some such embodiments, the
allowable rate of mode switching between dual polarized antenna
mode and single polarized antenna mode is less than the allowable
rate of switching between receive and transmit modes of
operation.
[0068] The flowchart of FIG. 3 has been described from the
perspective of an exemplary access node, e.g., base station, which
transmits pilot signals, and the flowchart of FIG. 2 has been
described from the perspective of an exemplary wireless terminal,
e.g., mobile node, which receives pilot signals. However, in some
embodiments, the roles are reversed and the wireless terminal
transmits uplink pilot signals which are received and used by the
base station. It should also be appreciated that in some
embodiments, the mode of antenna operation for an access node,
e.g., base station refers to a connection with a particular
wireless terminal, and in some such embodiments, from the access
node's perspective, the access node, e.g., base station can be in a
dual polarized mode of operation with regard to a first wireless
terminal being in a single polarized mode of operation with regard
to a second wireless terminal.
[0069] FIG. 4 illustrates an exemplary memory 400 which may be
memory 248 of wireless communications device 200 shown in FIG. 1.
The memory unit 400 is coupled to other elements via a bus, e.g.
bus 252 of FIG. 1, over which the various elements may interchange
data and information. Memory unit 400 includes routines 402 and
data/information 420. The routines 402 and the data/information 420
in memory unit 400 are used by a processor, e.g. a CPU, to control
the operation of a communication device, e.g. control
communications device 200 of FIG. 1, and implement methods, e.g.,
method of flowchart 100 of FIG. 2 or flowchart 300 of FIG. 3.
[0070] In some embodiments, some of the modules in memory 400 are
used in place of a corresponding module shown in FIG. 1. For
example, one embodiment may include SNR module 416 instead of SNR
sub-module 251. In some embodiments, some of the modules shown in
FIG. 1 are used in place of a corresponding module shown in FIG. 4.
For example, one embodiment may use rank sub-module 253 instead of
rank computation module 414. Thus some illustrated modules may
represent alternative embodiments. In some embodiments, for at
least some functions, a module shown in FIG. 1 operates in
coordination with a corresponding module in memory 400 to perform a
function or implement a step of a method. For example, in one
embodiment, output signaling control module 418 works in
conjunction with output signal module 249. Other modules shown in
the example of FIG. 1, such as modules 222, 220, 224, 226, 228,
230, 232, 234, 236, 238, 240, 247, and/or 249, are, in some
embodiments, replaced either wholly or in part by a module in
memory. Thus the techniques, functions, and/or steps of methods of
various embodiments may be implemented using software, hardware
and/or a combination of software and hardware.
[0071] Routines 402 include a communications routines 404 and
control routines 406. The communications routine 404 implements the
various communications protocols used by the communication device
including memory 400, e.g., communications device 200 of FIG. 1.
Control routines 406 include, an antenna switch control module 408,
an Rx/Tx switch control module 410, a pilot signal generation
module 412, a rank computation module 414, an SNR module 416 and an
output signaling control module 418. Data/information 420 includes
transmit data set 1 422, transmit data set 2 424, received data set
1 426, received data set 2 428, selected antenna mode information
430, channel quality information 432, current mode information 434,
channel quality indicator signal information 436, Rx/Tx timing
control information 438, and antenna polarization information
440.
[0072] The antenna switch control module 408 is used, in some
embodiments, to control the operation of an antenna switching
module, e.g. antenna switching module 208 of FIG. 1. The antenna
switch control module 408 controls the antenna switching operation
based on the information provided by selected antenna mode
information 430, is an output of antenna mode selection module 224.
When a certain mode of antenna mode is selected, the antenna switch
control module 408 sends a command signal to the antenna switching
module, e.g. switching module 208 of FIG. 1. Based on this control
command, the antenna switching module 208 may select either first
and second antennas or it may select first and third antennas. In
some other embodiments, the antenna mode selection module 224
generates the switching control signal directly which it sends to
the antenna switching module 208.
[0073] The Rx/Tx switch control module 410, in some embodiments,
controls the operation of the Rx/Tx switch module 210. Based on the
Rx/Tx timing control information 438, the Rx/Tx mode control module
408 sends a control signal to the Rx/Tx switching module 210, to
switch between receiver and transmitter modules, e.g. receiver
modules (214, 216) and transmitter modules (212, 218) of FIG. 1.
The Rx/Tx switch control module may be omitted in some embodiments,
for example in FDD embodiments.
[0074] The pilot signal generation module 412 generates the pilot
signals to be transmitted from a first communication device to a
second communication device. For example, consider that memory 400
is part of a base station, pilot signal generation module 412
generates pilot signals to be transmitted to a wireless terminal
using the base station as a point of attachment.
[0075] Rank computation module 414 is implemented in the memory 400
to compute rank information for the channel matrix between
transmitter antennas and receive antennas. The rank information is
computed based on the channel quality information, e.g. SNR or
multiple SNR values, interference level information, etc.
[0076] SNR module 416 determines SNRs corresponding to received
signals, e.g., a first SNR corresponding to a first pair of
antennas in a MIMO configuration and a second SNR corresponding to
a second pair of antennas in a MIMO configuration.
[0077] Output signaling control module 418 controls the operation
of output signal module 249, e.g., controlling embedding of channel
quality indicator signals, antenna mode indicator signals, other
control signals, and user data into data set 1 information and data
set 2 information.
[0078] Data/information 420 includes a plurality of set of stored
information, e.g. stored information set 442, indicating, e.g. base
station ID, sector identification values associated with the
various sectors of base station, antenna polarization information
etc. Stored information set 444 may include similar information,
e.g., corresponding to a different communications device.
Data/information 420 further includes information as data set 1 to
be transmitted 422, data set 2 to be transmitted 424, received data
set 1 information 426, stored received data set 2 information 428,
selected antenna mode information 430, channel quality information
432, e.g. SNRs, current mode information 434, i.e. the information
about current mode of antenna operation in the communications
device including memory 400, channel quality indicator signal
information 436, Rx/Tx timing control information 438, i.e.
information that controls as to when the communications device
including memory 400 will transmit and when it will receive.
Accordingly, the Rx/Tx switch control module 410 switches between
available receiver and transmitter modules as a function of
information 438. Data/information 420 also includes the antenna
polarization information 436 which includes information
characterizing and/or identifying polarization for each of the
available antennas, e.g. first, second and third antennas of the
device including memory 400, e.g., device 200 of FIG. 1.
[0079] FIG. 5 is a drawing of an exemplary communications system
500 including two wireless communications devices (502, 504) which
support MIMO operations and antenna switching, each device (502,
504) including two antennas polarized in a vertical direction and
an antenna polarized in a horizontal direction. Exemplary first
communications device 502 includes a antenna polarized in the
vertical direction 518, a 2.sup.nd antenna polarized in the
horizontal direction 520 and a third antenna polarized in the
vertical direction 522. Exemplary second communications device 504
includes a antenna polarized in the vertical direction 534, a
2.sup.nd antenna polarized in the horizontal direction 536 and a
third antenna polarized in the vertical direction 538.
[0080] First communications device 502 includes an encoder module
508 for encoding input data 540, a first RF chain 510, a 2.sup.nd
RF chain 512, an RF switch module 514 and an antenna selection
module 516. Second communications device 504 includes an RF switch
module 524, a first RF chain 526, a second RF chain 528 and a
decoder module 530 including an antenna selection module 532.
[0081] A wireless channel 506 exists between first and second
devices (502, 504). The wireless channel 506 may, and sometimes
does, change over time as a function of wireless device positions,
noise, interference, obstructions, weather conditions, etc.
[0082] The first and second communications devices (502, 504) may
be in accordance with exemplary communications device 200 or a
variation thereof. For example, with regard to 1.sup.st
communications device 502, encoder module 508 may be represented by
output signal module 249 in FIG. 1 RF chain 1 510 may be
represented by transmitter module 1 212 in FIG. 1, RE chain 2 512
may be represented by transmitter module 2 218 in FIG. 1 RF switch
module 514 may be represented by antenna switching module 208 in
FIG. 1, antenna selection module 516 may be represented by antenna
mode selection module 224 including antenna mode indicator signal
detection module 226 of FIG. 1, and antennas (518, 520, 522) may be
represented by antennas (202, 204, 206) of FIG. 1.
[0083] Continuing with the example, with regard to the 2.sup.nd
communications device 504, antennas (534, 536, 538) may be
represented by antennas (202, 204, 206), respectively of FIG. 1, RF
switch module 524 may be represent by antenna switching module 208
of FIG. 1, RF chain 1 526 may be represented by receiver module 1
214 of FIG. 1, RF chain 2 528 may be represented by receiver module
2 216 of FIG. 1, decoder module 530 may be represented by the
combination of: combining module 236, 1.sup.st symbol recovery
module 238, second symbol recovery module 240, channel quality
determination module 234, antenna mode selection module 224
including channel based antenna mode decision module 228, and
antenna mode indicator signal generation module 220 of FIG. 1.
[0084] In the example of FIG. 5, there is one input data stream 540
and one corresponding output data stream 542. In some embodiments,
there are multiple, e.g., two, input data streams and two output
data streams. White shown in the illustrated embodiment, with a
single data input and data output, in other embodiments, multiple
data input and data output streams are supported.
[0085] An exemplary strategy, used in this exemplary embodiment
will now be described. Consider that FIG. 5 illustrates a 2.times.2
MIMO link. The first device 502, which is to transmit the data
stream, includes two vertically polarized antennas (518, 522) and
one horizontally polarized antenna 520. The second device 504,
which is to recover the data stream, includes two vertically
polarized antennas (534, 538) and one horizontally polarized
antenna 536. Furthermore, the first device 502 includes two RF
chains (510, 512) and the second device includes two RF chains
(526, 528). The second device 504, which is the intended receiver,
implements a selection methodology which selects the antennas to be
used based on the observed SNR. If the SNR is greater than a
predetermined threshold, the selection methodology implementation
selects dual polarization mode. In other embodiments rank
information is used in addition to the SNR information in making
the mode selection decision. Commands are generated and sent to the
RF switch module 524 of the receiver device 504 and to the RF
switch module 514 of the 1.sup.st device 502, to use the dual
polarized configuration, e.g., antennas (536, 538) for the 2.sup.nd
device 504 and antennas (520, 522) for the 1.sup.st device 502.
Antenna selection module 532 makes the determination based on
measured SNR information. Switching control signal 544 communicates
the receive selection setting to RF switch module 524. Transmit
selection signal 546, e.g., a generated antenna mode selection
signal, is communicated from decoder module 530 to antenna
selection module 516 which detects the signal and sends a switching
control signal 548 to RF switch module 514. In some embodiments, a
control signal 550 indicating the antenna mode selection is also
sent to the encoder module 508 so that different encoding can be
used as a function of antenna mode selection.
[0086] However, if the SNR falls below the threshold, the
implemented methodology determines to command the first and second
devices (502, 504) to switch to the spatial array configuration, by
switching one of the RF chains from the horizontally polarized
antenna to the currently idle vertically polarized antenna. For
example, the switching results in the spatial array configuration
in which the 1.sup.st device 502 uses antennas (518 and 522) and
idles antenna 520, and the second device 504 uses antennas (53.4
and 538) and idles antenna 536. The switching information is
conveyed to the first device 502, which is the transmitter device
with regard to the data stream, by means of a low bandwidth
feedback channel (see signal 546). This strategy can be easily
generalized to a higher order MIMO configuration.
[0087] The threshold SNR for the selection methodology can be, and
sometimes is, selected based on the capacity. As shown in drawing
600 of FIG. 6, a dual polarized MIMO outperforms the rank deficient
spatial MIMO channel for SNR>6 dBs for one exemplary considered
configuration. In various embodiments, a back-off is applied to
this value to account for implementation tosses, when determining a
threshold used for selecting between dual and single polarization
modes of operation. In propagation scenarios, where the spatial
MIMO channel achieves full rank or nearly full rank and is
sufficiently de-correlated as shown in FIG. 6, the dual polarized
MIMO configuration does not offer any benefit. The proposed
strategy can be easily modified to accommodate these scenarios as
well, e.g., by using determined rank information in the antenna
selection decision.
[0088] The spatial MIMO configuration enjoys a power benefit over
its dual polarized counterpart. This power benefit does not depend
upon the inter-element spacing used to realize the antenna array.
Thus, the two vertically polarized antennas on a mobile device do
not need to be separated by a large distance,
[0089] In some embodiments, the proposed strategy is used to
increase the capacity of high SNR users in a cellular network with
only a nominal increase in complexity and cost. The capacity of
high signal to noise ratio users is limited by the degrees of
freedom whereas the capacity of low SNR users is limited by
received signal power. Hence the dual polarized MIMO configuration
is suitable for users in the high SNR regime whereas the spatial
array configuration is preferred for the low SNR users. An
exemplary proposed strategy selects the appropriate MIMO
configuration depending on the operating SNR.
[0090] FIG. 7 includes a drawing 700 illustrating an exemplary
sequence of intervals (evaluation interval 702, data interval 704,
evaluation interval 706, data interval 708, evaluation interval
710, data interval 712, evaluation interval 714, . . . ) in an
exemplary timing structure in accordance with one exemplary
embodiment. In some embodiments, no traffic data signals, e.g., no
user data signals, are communicated in the evaluation intervals.
The exemplary sequence of intervals may be used, for example, in a
communications device implementing the method of flowchart 100 of
FIG. 1. In this exemplary embodiment, the communications device
remains in a selected mode, e.g., one of a single polarization mode
and dual polarization mode, during a data interval, and the
communications device receives and evaluates pilot signals during
the data interval in the selected mode, said pilot signals being
communicated in addition to traffic signals during the data
interval. However, at the end of a data interval, the
communications device switches to the opposite mode of operation,
so that it may evaluate pilot signals communicated in the other
mode during a subsequent evaluation interval. Then, following the
evaluation interval, the communications device makes a decision as
to the selected mode for the next data interval and has an
opportunity to switch modes. The decision as to which mode to use
for the data interval, in some embodiments, is base on pilot
signals received during the previous data interval and pilot
signals received during the evaluation interval. Information such
as estimated SNRs and/or rank information is used to make the
decision.
[0091] Arrows (716, 720, 724, 728) identify channel estimation
based switching opportunities with the decision of the switching
being implemented for the following data interval (704, 708, 712),
respectively. Arrows (718, 722, 726) identify points for mode
switching such that the communications device may evaluate channel
conditions in the other mode than was previously used in the prior
data interval (704, 708, 714), respectively.
[0092] Drawing 750 illustrates one example illustrating mode
switching for evaluation purposes and mode switching based on
channel estimation information. Block 752 indicates that the
communications device in operated in the single polarization mode
of operation, e.g., receiving pilot signals from two vertical
polarized antennas, during interval 702 which is an initial
evaluation interval. Channel quality, e.g., SNRs and/or rank
information is determined based on the received pilot signals. At
point 716, the communications device makes a decision to switch to
the dual polarized mode of operation and switches into the dual
polarized mode of operation. During data interval 704, the
communications device remains in the dual polarized mode of
operation as indicated by block 754. During the dual polarized mode
of operation the communications device receives pilot signals from
antennas in two different polarization directions, e.g., from a
vertical polarized antenna and from a horizontal polarized
antennas. Then, at time 718 the communications device switches to
the single polarized mode of operation. Block 756 indicates that
the communications device operates in the single polarized mode of
operation during evaluation interval 706, e.g., receiving pilot
signals from two vertically polarized antennas. Based on channel
conditions, the communications device decides to remain in the
single polarized mode of operation, and therefore does not switch
at point 720. The communications device remains in the selected
single polarization mode during data interval 708 as indicated b
block 758 and receives pilot signals during this interval, e.g.,
from two vertically polarized antennas.
[0093] At point 722, the communications device switches to the dual
polarized mode for the evaluation interval 710 as indicated by
block 760, and the communications device receives pilot signals
from both a first and second polarization direction antennas. In
this case at switching opportunity 724, the communications device
selects dual polarized mode, so the device remains in the dual
polarized mode for data interval 712 as indicated by block 762.
Pilot signals are received on both direction polarization antennas
during data interval 712. Then at time 726, the communications
device switches to the other mode, which is the single polarization
mode, and the single polarization mode is used for evaluation
interval 714 as indicated by block 764. The communications device
makes and implements another switching decision at point 728.
[0094] In some other embodiments, the communications device sets
the mode to the single polarization mode for each evaluation
interval, e.g., irrespective of the mode setting in the prior data
interval. In some embodiments, the communications device evaluates
both modes during the evaluation interval, e.g., being controlled
to be in the single polarization mode during a first potion of the
evaluation interval and being controlled to be in a dual polarized
mode during a second portion of the evaluation interval.
[0095] FIG. 8 includes a drawing 800 illustrating an exemplary
sequence of intervals (evaluation interval 802, data interval 804,
evaluation interval 806, data interval 808, evaluation interval
810, data interval 812, evaluation interval 814, . . . ) in an
exemplary timing structure in accordance with one exemplary
embodiment. In some embodiments, no traffic data signals, e.g., no
user data signals, are communicated in the evaluation intervals.
The exemplary sequence of intervals may be used, for example, in a
communications device implementing the method of flowchart 100 of
FIG. 1.
[0096] In this exemplary embodiment, the base station transmits
Single polarized pilots in some evaluation periods and Dual
polarized pilots in other evaluation periods, e.g., in accordance
with in a predetermined pattern. The pilots transmitted by the base
station during the evaluation periods are available to be used by a
plurality of mobiles. One exemplary predetermined pattern specifies
that the transmission is to alternate between single polarized
pilots and dual polarized pilots for successive evaluation periods
within a recurring timing structure.
[0097] The communications device, e.g., mobile wireless terminal,
which is to receive and evaluate the pilots, is aware of the
predetermined pattern being used for transmission and thus
configures its mode of operation in accordance with the specified
mode corresponding to the particular evaluation interval.
[0098] In this exemplary embodiment, the communications device
remains in a selected mode, e.g., one of a single polarization mode
and dual polarization mode, during a data interval, and the
communications device receives and evaluates pilot signals during
the data interval in the selected mode, said pilot signals being
communicated in addition to traffic signals during the data
interval. However, at the end of a data interval, the
communications device is set to a mode of operation in accordance
with a predetermined pattern corresponding to the evaluation
intervals, so that it may evaluate pilot signals communicated in
the specified mode for the particular evaluation interval. The
communications device switches modes if the specified mode for the
evaluation interval is different from the prior data interval.
[0099] Then, following the evaluation interval, the communications
device makes a decision as to the selected mode for the next data
interval and has an opportunity to switch modes. The decision as to
which mode to use for the data interval, in some embodiments, is
based on pilot signals received during the previous data interval
and/or pilot signals received during the evaluation interval.
Information such as estimated SNRs and/or rank information is used
to make the decision,
[0100] Arrows (816, 820, 824, 828) identify channel estimation
based switching opportunities with the decision of the switching
being implemented for the following data interval (804, 808, 812),
respectively. Arrows (818, 822, 826) identify points for mode
setting such that the communications device may evaluate channel
conditions in the mode specified in accordance with the
predetermined pattern being used for evaluation periods.
[0101] Drawing 850 illustrates one example illustrating mode
setting for evaluation purposes and mode switching based on channel
estimation information. In this example the mode setting alternates
for successive evaluation intervals. Block 852 indicates that the
communications device in operated in the single polarization mode
of operation, e.g., receiving pilot signals from two vertically
polarized antennas, during interval 802 which is an initial
evaluation interval. Channel quality, e.g., SNRs and/or rank
information is determined based on the received pilot signals. At
point 816, the communications device makes a decision to switch to
the dual polarized mode of operation and switches into the dual
polarized mode of operation. During data interval 804, the
communications device remains in the dual polarized mode of
operation as indicated by block 854. During the dual polarized mode
of operation the communications device receives pilot signals from
antennas in two different polarization directions, e.g., from a
vertical polarized antenna and from a horizontal polarized
antenna.
[0102] Then, at time 818 the communications device is set to the
dual polarized mode of operation in accordance with the
predetermined evaluation interval pattern. In this case the
wireless terminal remains in the dual mode, since it happened to be
in dual polarized mode during the prior data interval. In some
embodiments, the wireless terminal can choose to ignore an
evaluation interval, such as interval 806, in which the
predetermined specified mode for the evaluation interval is the
same as the previous data interval mode, because it can evaluate
pilots from the data interval window. Thus in such a scenario, the
wireless terminal may, and sometimes does, conserve power or
perform a different function during such an evaluation
interval.
[0103] Block 856 indicates that the communications device operates
in the dual polarized mode of operation during evaluation interval
806, e.g., receiving pilot signals from both a first and second
polarization direction antennas. Since data interval 804 and
evaluation interval 806 were both in dual mode, the communications
device remains in the selected dual polarization mode during next
data interval 808 as indicated by block 858 and receives pilot
signals during this interval, e.g., from both first and second
polarization direction antennas.
[0104] At point 822, the communications device switches to the
single polarized mode for the evaluation interval 810 as indicated
by block 860, and the communications device receives pilot signals
from two vertically polarized antennas. In this case at switching
opportunity 824, the communications device selects single polarized
mode, so the device is set to the single polarized mode for data
interval 812 as indicated by block 862. Pilot signals are received
on the two vertically polarized antennas during data interval 812.
Then at time 826, the communications device switches to the dual
polarization mode in accordance with the predetermined pattern
being used of the evaluation intervals, and the dual polarization
mode is used for evaluation interval 814 as indicated by block 864.
The communications device makes and implements another switching
decision at point 828.
[0105] In some other embodiments, the communications device sets
the mode to the single polarization mode for each evaluation
interval, e.g., irrespective of the mode setting in the prior data
interval. In some embodiments, the communications device evaluates
both modes during the evaluation interval, e.g., being controlled
to be in the single polarization mode during a first potion of the
evaluation interval and being controlled to be in a dual polarized
mode during a second portion of the evaluation interval.
[0106] The techniques of various embodiments may be implemented
using software, hardware and/or a combination of software and
hardware. Various embodiments are directed to apparatus, e.g.,
mobile nodes such as mobile terminals, base stations,
communications system. Various embodiments are also directed to
methods, e.g., method of controlling and/or operating mobile nodes,
base stations and/or communications systems, e.g., hosts. Various
embodiments are also directed to machine, e.g., computer, readable
medium, e.g., ROM, RAM, CDs, hard discs, etc., which include
machine readable instructions for controlling a machine to
implement one or more steps of a method.
[0107] In various embodiments nodes described herein are
implemented using one or more modules to perform the steps
corresponding to one or more methods, for example, signal
processing, a decision step, message generation, message signaling,
switching, reception and/or transmission steps. Thus, in some
embodiments various features are implemented using modules. Such
modules may be implemented using software, hardware or a
combination of software and hardware. Many of the above described
methods or method steps can be implemented using machine executable
instructions, such as software, included in a machine readable
medium such as a memory device, e.g., RAM, floppy disk, etc. to
control a machine, e.g., general purpose computer with or without
additional hardware, to implement all or portions of the above
described methods, e.g., in one or more nodes. Accordingly, among
other things, various embodiments are directed to a
machine-readable medium including machine executable instructions
for causing a machine, e.g., processor and associated hardware, to
perform one or more of the steps of the above-described method(s).
Some embodiments are directed to a device, e.g., communications
device, including a processor configured to implement one, multiple
or all of the steps of one or more methods of the invention.
[0108] In some embodiments, the processor or processors, e.g.,
CPUs, of one or more devices, e.g., communications devices such as
wireless terminals are configured to perform the steps of the
methods described as being as being performed by the communications
device. Accordingly, some but not all embodiments are directed to a
device, e,g., communications device, with a processor which
includes a module corresponding to each of the steps of the various
described methods performed by the device in which the processor is
included. In some but not all embodiments a device, e.g.,
communications device, includes a module corresponding to each of
the steps of the various described methods performed by the device
in which the processor is included. The modules may be implemented
using software and/or hardware.
[0109] While described in the context of an OFDM system, at least
some of the methods and apparatus of various embodiments are
applicable to a wide range of communications systems including many
non-OFDM and/or non-cellular systems.
[0110] Numerous additional variations on the methods and apparatus
of the various embodiments described above will be apparent to
those skilled in the art in view of the above description. Such
variations are to be considered within the scope. The methods and
apparatus may be, and in various embodiments are, used with CDMA,
orthogonal frequency division multiplexing (OFDM), and/or various
other types of communications techniques which may be used to
provide wireless communications links between access nodes and
mobile nodes. In some embodiments the access nodes are implemented
as base stations which establish communications links with mobile
nodes using OFDM and/or CDMA. In various embodiments the mobile
nodes are implemented as notebook computers, personal data
assistants (RDAs), or other portable devices including
receiver/transmitter circuits and logic and/or routines, for
implementing the methods.
* * * * *